And Java typically does produce both (see Exception "cause" field). So when an exception stack trace is printed it's actually list of stacktraces, for each "cause". You can skip stacktraces and just concatenate causes' messages (like people often do in Go).

So the full message would be like "Cannot add item X to cart Y: Error connecting to warehouse Z: Error establishing TLS connection to example.com 127.0.1.1: PKIX failed".